PREDICTING PRODUCTS FOR EQUATIONS (PROBLEM # 4, Part B)
You will get THREE reactions, you must predict the products for each and answer a short
question. Remember to:
I.
Use lowest whole number coefficients to balance the equations
II.
Represent substances in solution as ions (leave out spectators!)
III.
You DO NOT need to list any states of matter.
2010A
2010B
2009A
2009B
2008A
2008B
2007A
2007B
(a)
Acid-Base
Decomp. of a Hydrate
Single Rep./Redox
Double Rep. (Precipitate)
Complex ion
Single Rep./Redox
Double Rep. (Precipitate)
Decomposition
(b)
Combustion
Complex ion
Acid-Base
Redox (metal exchange)
Single Rep./Redox
Acid-Base
Acid-Base
Single Rep./Redox
(c)
Decomposition
Acid-Base
Decomposition
Double Rep. (Hydrolysis)
Double Rep. (Grp. 1 oxide)
Double Rep. (precipitate)
Redox (metal exchange)
Single Rep (Group I)
2011A
(a) Zinc metal is added to a hydrobromic acid solution.
(i) Balanced equation:
(ii) Write the oxidation half-reaction for the reaction.
(b) Solid lithium oxide is added to distilled water.
(i) Balanced equation:
(ii) Indicate whether the pH of the resulting solution is less than 7, equal to 7, or greater
than 7. Explain.
(c) A 100 mL sample of 1 M strontium chloride solution is mixed with a 100 mL sample of 1 M
sodium carbonate solution, resulting in the formation of a precipitate.
(i) Balanced equation:
(ii) Describe what will occur if the precipitate is dried and a few drops of 1 M hydrochloric
acid are added. Explain.
Answer:
(a) (i) Zn + 2 H+  Zn2+ + H2
(ii) Zn – 2 e-  Zn2+
(b) (i) Li2O + H2O  2 Li+ + 2 OH–
(ii) >7; hydroxide ion is a strong base; metal oxides are basic anhydrides
(c) (i) Sr2+ + CO32–  SrCO3
(ii) fizzing; H+ + SrCO3  Sr2+ + H2O + CO2 gas is formed
2011B
(a) Solid magnesium hydroxide is added to a solution of hydrobromic acid.
(i) Balanced equation:
(ii) What volume, in mL, of 2.00 M hydrobromic acid is required to react completely with
0.10 mol of solid magnesium hydroxide?
(b) Excess hydrochloric acid is added to a solution of cobalt(II) nitrate to produce a
coordination complex.
(i) Balanced equation:
(ii) Which species in the reaction acts as a Lewis base?
(c) A copper wire is dipped into a solution of silver(I) nitrate.
(i) Balanced equation:
(ii) Describe what is observed as the reaction proceeds.
Answer:
(a) (i) Mg(OH)2 + 2 H+  Mg2+ + 2 H2O
(ii) 0.10 L
(b) (i) 4 Cl– + Co2+  [CoCl4]2–
(ii) Cl–
(c) (i) Cu + 2 Ag+  Cu2+ + 2 Ag
(ii) wire will grow (...become coated with...) silver whiskers and the solution will become
blue-green
2010A
4. (a)
A 0.2 M potassium hydroxide solution is titrated with a 0.1 M nitric acid solution.
(i) Balanced equation:
(ii) What would be observed if the solution was titrated well past the equivalence point
using bromthymol blue as the indicator? (Bromthymol blue is yellow in acidic solution
and blue in basic solution.)
(b) Propane is burned completely in excess oxygen gas.
(i) Balanced equation:
(ii) When the products of the reaction are bubbled through distilled water, is the resulting
solution neutral, acidic, or basic? Explain.
(c) A solution of hydrogen peroxide is heated, and a gas is produced.
(i) Balanced equation:
(ii) Identify the oxidation state of oxygen in hydrogen peroxide.
Answer:
(a) (i) OH- + H+  H2O
(ii) the solution would be yellow
(b) (i) C3H8 + 5 O2  3 CO2 + 4 H2O
(ii) acidic, carbon dioxide is an acid anhydride and forms carbonic acid in water
(c) (i) 2 H2O2  2 H2O + O2
(ii) -1
2010 form B
4.
(a)
Solid copper(II) sulfate pentahydrate is gently heated.
(i) Balanced equation:
(ii) How many grams of water are present in 1.00 mol of copper(II) sulfate pentahydrate?
(b) Excess concentrated aqueous ammonia is added to a solution of nickel(II) nitrate, leading to
the formation of a complex ion.
(i) Balanced equation:
(ii) Which of the reactants acts as a Lewis acid?
(c) Methylamine (CH3NH2) is added to a solution of hydrochloric acid.
(i) Balanced equation:
(ii) Methylamine dissolves in water to form a solution. Indicate whether this solution is
acidic, basic, or neutral.
Answer:
(a) (i) CuSO4•5H2O  CuSO4 + 5 H2O
(ii) (5 mol)(18 g mol-1) = 90 g
(b) (i) Ni2+ + 6 NH3  [Ni(NH3)6]2+
(ii) Ni2+
(c) (i) CH3NH2 + H+  CH3NH3+
(ii) basic
2009(Form A)
4.
For each of the following three reactions, in part (i) write a balanced equation for the reaction and in part (ii)
answer the question about the reaction. In part (i), coefficients should be in terms of lowest whole numbers.
Assume that solutions are aqueous unless otherwise indicated. Represent substances in solutions as ions if the
substances are extensively ionized. Omit formulas for any ions or molecules that are unchanged by the
reaction. You may use the empty space at the bottom of the next page for scratch work, but only equations that
are written in the answer boxes provided will be graded.
(a)
A sample of solid iron(III) oxide is reduced completely with solid carbon.
(b)
(c)
(i)
Balanced equation:
(ii)
What is the oxidation number of carbon before the reaction, and what is the oxidation number of carbon
after the reaction is complete
Equal volumes of equimolar solutions of ammonia and hydrochloric acid are combined.
(i)
Balanced equation:
(ii)
Indicate whether the resulting solution is acidic, basic, or neutral. Explain.
Solid mercury(II) oxide decomposes as it is heated in an open test tube in a fume hood.
(i)
Balanced equation:
(ii)
After the reaction is complete, is the mass of the material in the test tube greater than, less than, or equal
to the mass of the original sample? Explain.
Answer:
(a) (i) 2 Fe2O3 + 3 C  4 Fe + 3 CO2
(ii) before C = 0, after C = +4
(b) (i) NH3 + H+  NH4+
(ii) acidic; the salt of a weak base is acidic
(c) (i) 2 HgO  2 Hg + O2
(ii) less; gaseous oxygen escapes from the test tube
2008(Form A)
4.
(a)
(b)
(c)
Aqueous sodium hydroxide is added to a saturated solution of aluminum hydroxide, forming a complex ion.
(i)
Balanced equation:
(ii)
If the resulting mixture is acidified, would the concentration of the complex ion increase, decrease, or
remain the same? Explain.
Hydrogen chloride gas is oxidized by oxygen gas.
(i)
Balanced equation:
(ii)
If three moles of hydrogen chloride gas and three moles of oxygen gas react as completely as possible,
which reactant, if any, is present in excess? Justify your answer.
Solid potassium oxide is added to water.
(i)
Balanced equation:
(ii)
If a few drops of phenolphthalein are added to the resulting solution, what would be observed? Explain.
ANSWERS:
(a) (i) Al(OH)3 + OH-  [Al(OH)4](ii) decrease; H+ will neutralize OH- and destroy the complex
(b) (i) 2 HCl + O2  H2O + OCl2 or 4 HCl + O2  2 H2O + 2 Cl2
(ii) O2 in excess; reacting on a 2:1 mole ratio, 3 mol HCl requires only 1.5 mol of O2
(c) (i) K2O + H2O  2 K+ + 2 OH(ii) pink color; phenolphthalein is pink in an alkaline solution
2007(Form A)
4.
(a)
(b)
(c)
A solution of sodium hydroxide is added to a solution of lead(II) nitrate.
(i)
Balanced equation:
(ii)
If 1.0 L volumes of 1.0 M solutions of sodium hydroxide and lead(II) nitrate are mixed together, how
many moles of product(s) will be produced? Assume the reaction goes to completion.
Excess nitric acid is added to solid calcium carbonate.
(i)
Balanced equation:
(ii)
Briefly explain why statues made of marble (calcium carbonate) displayed outdoors in urban areas are
deteriorating.
A solution containing silver(I) ion (an oxidizing agent) is mixed with a solution containing iron(II) ion (a
reducing agent).
(i)
Balanced equation:
(ii)
If the contents of the reaction mixture described above are filtered, what substance(s), if any, would
remain on the filter paper.
Answer:
(a) (i) 2 OH– + Pb2+  Pb(OH)2
(ii) Since hydroxide:lead hydroxide is in a 2:1 ratio, then ½ mol product is produced
(b) (i) 2 H+ + CaCO3  Ca2+ + H2O + CO2
(ii) The marble is dissolved (and reacts with) by the acid rain in the urban environment
(c) (i) Ag+ + Fe2+  Ag + Fe3+
(ii) solid silver
2007 (form B)
4.
(a)
(b)
(c)
Solid ammonium carbonate decomposes as it is heated.
(i)
Balanced equation:
(ii)
Predict the algebraic sign of ∆S˚ for the reaction. Explain your reasoning.
Chlorine gas, an oxidizing agent, is bubbled into a solution of potassium bromide.
(i)
Balanced equation:
(ii)
What is the oxidation number of chlorine before the reaction occurs? What is the oxidation number of
chlorine after the reaction occurs?
A small piece of sodium is placed in a beaker of distilled water.
(i)
Balanced equation:
(ii)
The reaction is exothermic, and sometimes small flames are observed as the sodium reacts with the
water. Identify the product of the reaction that burns to produce the flames.
Answer:
(a) (i) (NH4)2CO3  2 NH3 + H2O + CO2
(ii) positive, an increase in entropy as a solid converts into a mixture of gases
(b) (i) Cl2 + 2 Br–  2 Cl– + Br2
(ii) before 0, after -1
(c) (i) Na + H2O Na+ + OH– + H2
(ii) hydrogen gas